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United States Patent |
5,174,107
|
Ogawa
,   et al.
|
December 29, 1992
|
Combined power generating plant
Abstract
The present invention has been realized in order to treat noxious and
combustible gases, which are exhausted during the start-up operation of a
composite coal gasification-power plant and/or released from various
safety valves arranged in such power plant and which have hitherto been
discharged without treatment into the atmosphere, to make it innoxious and
to attain an efficient energy utilization and concerns an improvement of
such a composite coal gasification-power plant, which is characterized
either in that an additional combustion unit is disposed parallel to the
burner of the gas-turbine electric power generating unit and is arranged
so as to supply the combustion exhaust gas of this additional combustion
unit to as to supply the combustion exhaust gas of this additional
combustion unit to the waste heat boiler, or in that an additional
combustion unit, operative to effect to burn the noxious and combustible
gases exhausted from the burner during start-up and/or those released from
safety valves arranged in the power plant and to supply the combustion
exhaust gas to said waste heat boiler, is arranged.
Inventors:
|
Ogawa; Kiichiro (Tokyo, JP);
Osawa; Yasuko (Tokyo, JP);
Miyake; Junsuke (Tokyo, JP)
|
Assignee:
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Mitsubishi Jukogyo Kabushiki Kaisha (Tokyo, JP)
|
Appl. No.:
|
891662 |
Filed:
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May 29, 1992 |
Foreign Application Priority Data
Current U.S. Class: |
60/39.12; 60/39.182; 122/7B |
Intern'l Class: |
F02B 043/00; F02B 003/00 |
Field of Search: |
60/39.12,39.182
122/7 B
|
References Cited
U.S. Patent Documents
3731485 | May., 1973 | Rudolph et al. | 60/39.
|
4238923 | Dec., 1980 | Waryasz.
| |
4472936 | Sep., 1984 | Uchiyama et al. | 60/39.
|
4489562 | Dec., 1984 | Snyder et al.
| |
4831817 | May., 1989 | Linhardt.
| |
4896499 | Jan., 1990 | Rice | 60/39.
|
Foreign Patent Documents |
2047265 | Nov., 1990 | GB.
| |
Other References
2448 Progress in Energy and Combustion Science vol. 8 (1982) No. 4, Oxford,
Great Britain.
|
Primary Examiner: Koczo; Michael
Assistant Examiner: Richman; Howard R.
Attorney, Agent or Firm: Anderson Kill Olick & Oshinsky
Parent Case Text
This is a continuation application of Ser. No. 07/549,450, filed Jul. 6,
1990, now abandoned.
Claims
We claim:
1. A combined power generating plant, comprising:
a coal gasifying furnace;
gas cooler means for recovering sensible heat of gas produced in the coal
gasifying furnace by generating steam with the heat so recovered;
gas purification means for removing impurities contained in the so cooled
gas;
a gas-turbine electric power generating unit having a burner for burning
the gas purified in the gas purification means;
waste heat boiler means for generating steam by recovering the sensible
heat contained in exhaust gas from said gas-turbine electric power
generating unit;
a steam-turbine electric power generating unit fed by the steam from said
gas cooler and from said waste heat boiler; and
a catalyst burning system disposed between said gas purification means and
said waste heat boiler means parallel to said burner of the gas-turbine
electric power generating unit so as to burn combustible waste gases
produced in the gasifying furnace during the start-up operation of the
plant and so that catalytically burned exhaust gas is supplied to said
waste heat boiler means.
2. A combined power generating plant as claimed in claim 1, and further
comprising valves connected to exhaust gas outlets of the coal
gasification furnace, the gas cooler and the gas purification unit so as
to cause exhaust gas to flow to said catalyst burning system disposed
parallel to said burner of the gas-turbine electric power generating unit.
Description
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a composite coal gasification-power plant
and, in particular, to a technical means for treating noxious and
combustible gases appearing during start-up operation of such power plant
and/or those released from safety valves arranged in such plant so as to
deprive dangers and toxicity of these gases.
A typical layout of conventional composite coal gasification-power plant is
shown in FIG. 3. The plant of FIG. 3 includes a coal gasifying furnace 1,
which is fed by coal and gasifying agents, such as, air, oxygen, steam and
so on, to cause reaction between them under a condition of high
temperature and high pressure to produce a fuel gas composed mainly of
carbon monoxide and hydrogen. The so produced gas is passed to a gas
cooler 2 composed of a set of heat exchangers employed for sucking up the
sensible heat contained in the gas to the cooling water to thereby
generate steam in order to attain an efficient heat utilization. The gas
so cooled is then passed to a gas purification unit 3 composed of a dust
separator, desulfurizer and so on to remove impurities in the gas, such
as, dust, sulfur oxides and so on. The thus cleaned gas is then fed to a
burner 4 to burn it. The combustion gas therefrom is then discharged into
a gas turbine 5 to drive a power generator 6 and an air compressor 7.
These elements 4,5,6 and 7 constitute a gas-turbine power generation unit.
The hot exhaust gas from the gas-turbine power generation unit is sent to a
waste heat boiler 8 where it delivers its heat to water to generate steam,
whereupon the spent gas is exhausted to the atmosphere through a chimney
9. The steam generated in the waste heat boiler 8 is fed, together with
the steam generated in the gas cooler 2, to a steam turbine 10 in a
steam-turbine power generation unit to drive a power generator 11.
In the conventional composite coal gasification-power plant as explained
above, the product gas of the coal gasifying furnace 1 produced in the
start-up period of the furnace operation appears also as a noxious gas due
to contents of noxious and combustible gas components, until the running
conditions and the gas composition will reach a steady state and the gas
will be ready for combustion by the burner, so that release of these
noxious gases as such into the atmosphere is undesirable in the point of
view of environmental sanitation.
In the practice of the stand of technique, the warming-up operation of the
coal gasifying furnace 1 and the gas purification unit 3 has been realized
while burning out the noxious combustible gases produced during this
warming-up period by a separately arranged gas-burning-out furnace (or a
flare stack) 12, as shown in FIG. 3.
In a composite coal gasification-power plant, various safety means, such
as, safety valves 13, pressure control valves 14, gas relief valves (not
shown) and so on, are usually installed for security confirmation, as
shown in FIG. 3. When these safety means are put into operation on
occasion, noxious and combustible gases may be discharged as such into the
atmosphere, which is also undesirable. In the conventional practice, the
gases released from these safety means are collected in a pressure vessel
15, from which they are sent to the gas-burning-out furnace 12 mentioned
above to subject to burning treatment. The so burnt waste gas from the
gas-burning-out furnace 12 is then discharged into the chimney 9 through a
gas cooler 16 disposed between the gas-burning-out furnace 12 and the
chimney 9.
In the stand of technique as described above, a special monitoring means
for observation of the burning condition of the gas-burning-out furnace
and, in a special occasion, even a combustion assisting means may be
required, since the gases from the safety means contain, in general,
combustible components only in a low concentration with considerable
fluctuation of the gas composition resulting from the warming-up operation
of the coal gasifying furnace.
In addition, a possible secondary environmental pollution from the gas
burning-out treatment due to occurrence of so-called thermal nitrogen
oxides may bring about necessity of further installation for the removal
of them. The theoretical relationship between the amount of thermal
nitrogen oxides occurring after 0.5 second of the reaction and the
temperature therefor is as given in FIG. 4. As is seen, the amount of
occurrence of the thermal nitrogen oxides tends to increase steeply above
1600.degree. C.
In the practice, it takes usually several hours for a warming-up operation
of the coal gasifying furnace 1 and of the gas purification unit 3 of a
composite coal gasification-power plant, depending on the scale of the
plant, while operating the gas-burning-out furnace 12 or the flare stack,
causing thus a considerable loss of thermal energy with the increase of
number of repeated warming-up operations.
OBJECT AND SUMMARY OF THE INVENTION
The first aspect of the present invention is directed to the solution of
the problems of the stand of technique described above, by providing a
composite coal gasification-power plant, which comprises a coal gasifying
furnace, a gas cooler operative to recover the sensible heat of the gas
produced in the coal gasifying furnace by generating steam by the heat so
recovered, a gas purification unit operative to remove impurities
contained in the so cooled gas, a gas-turbine electric power generating
unit having a burner for burning the gas purified in the gas purification
unit, a waste heat boiler operative to recover the heat contained in the
exhaust gas from said gas turbine by generating steam by the so recovered
heat and a steam-turbine electric power generating unit fed by the steams
from said gas cooler and from said waste heat boiler, characterized in
that said composite power plant further comprises an additional combustion
unit disposed parallel to said burner of the gas-turbine power generating
unit and arranged operative to burn out the gas turbine exhaust gas during
the start-up operation of the plant and to supply its combustion exhaust
gas to said waste heat boiler.
The subject matter of the second aspect of the present invention is a
composite coal gasification-power plant, which comprises a coal gasifying
furnace, a gas cooler operative to recover the sensible heat of the gas
produced in the coal gasifying furnace by generating steam by the heat so
recovered, a gas purification unit operative to remove impurities
contained in the so cooled gas, a gas-turbine electric power generating
unit having a burner for burning the gas purified in the gas purification
unit, a waste heat boiler operative to recover the heat contained in the
exhaust gas from said gas turbine by generating steam by the so recovered
heat and a steam-turbine electric power generating unit fed by the steams
from said gas cooler and from said waste heat boiler, characterized in
that said composite power plant further comprises an additional combustion
unit operative to effect to burn out the gas tubine exhaust gas during the
start-up operation of the plant and/or released gases from safety valves
arranged in the power plant and to supply the combustion exhaust gas to
said waste heat boiler.
According to the first aspect of the present invention, the noxious and
combustible gases produced during the warming-up operation of a composite
coal gasification-power plant are burnt out in an additional combustion
unit to make them innoxious and the sensible heat contained in the
combustion gas is recovered in a waste heat boiler in order to attain an
efficient energy utilization.
According to the second aspect of the present invention, the noxious and
combustible gases exhausted from the burner of a gas turbine during the
start-up of the plant and/or those released from safety valves arranged in
a composite coal gasification-power plant upon their operation are burnt
in an additional combustion unit to make them innoxious and the sensible
heat contained in the combustion gas is recovered in a waste heat boiler.
Thus, by the first aspect of the present invention, it is made possible to
treat the noxious and combustible gases occurring in a composite coal
gasification-power plant into innoxious state in a practical and
economical way under attainment of utilization of the heat energy which
has hitherto been discarded without making use of into the atmosphere with
simultaneous environmental preservation, and thus, a practical and
economical composite coal gasification-power plant is provided, since the
noxious and combustible gases produced from the coal gasifying furnace
during start-up operation thereof are burnt in an additional combustion
unit disposed parallel to the burner of the gas turbine and the sensible
heat of the combustion gas therefrom is recovered in the waste heat
boiler.
According to the second aspect of the present invention, it is made
possible to treat the gases released from various safety valves in a
composite coal gasification-power plant in a practical and economical way
into innoxious state under attainment of utilization of the heat energy
which has hitherto been abandoned without making use of it into the
atmosphere with simultaneous environmental preservation, and thus, a
practical and economical composite coal gasification-power plant is
provided, since the noxious and combustible gases released from the safety
valves upon occasional operation thereof are burnt out in the additional
combustion unit to make them innoxious and the sensible heat of the
combustion gas exhausted therefrom is recovered in the waste heat boiler.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an embodiment of the composite coal gasification-power plant
according to the present invention in a flow sheet.
FIG. 2 is a flow sheet of another embodiment of the composite coal
gasification-power plant according to the present invention.
FIG. 3 shows a conventional composite coal gasification-power plant also in
flow sheet.
FIG. 4 shows the theoretical relationship between the formation of thermal
nitrogen oxides and the reaction temperature.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Below, the present invention is further described by way of Examples with
reference to the appended Drawings.
In FIG. 1, there is shown an Example of the composite coal
gasification-power plant of the first aspect of the present invention,
wherein the same reference numerals are employed for identical parts as in
FIG. 3.
As shown in FIG. 1, coal is charged to a coal gasifying furnace 1 to
produce a fuel gas which is fed to a gas cooler 2 operative to cool the
fuel gas under generation of steam. A gas purification unit 3 serves for
removing impurities contained in the fuel gas cooled in the cooler 2. The
so cleaned gas is then fed to a burner 4 for a gas turbine 5 and is burnt
therein to produce hot exhaust gas which is discharged into the gas
turbine 5 to drive it. The gas turbine 5 drives a power generator 6 and an
air compressor 7. These elements 4, 5, 6 and 7 constitute a gas-turbine
electric power generation unit. 8 is a waste heat boiler for recovering
the heat energy in the gas turbine exhaust gas from the gas-turbine power
generating unit to generate steam. The waste gas from the waste heat
boiler 8 is discharged into the atmosphere through a chimney 9. The steams
generated in the waste heat boiler 8 and in the gas cooler 2 are utilized
to rotate a steam turbine 10 for driving a power generator 11. The
function and operation of these elements 1 to 11 are identical with those
explained already with respect to FIG. 3 and the explanation therefor is,
therefore, omitted.
In FIG. 1, the additional combustion unit to be incorporated in the
composite coal gasification-power plant according to the first aspect of
the present invention is shown at 21. The additional combustion unit 21 is
disposed between the outlet of the gas purification unit 3 and the inlet
of the waste heat boiler 8 parallel to the burner 4 of the gas turbine.
The feed line 22 supplying combustion air to the additional combustion
unit 21 is branched out from a connection line connecting the air
compressor 7 and the burner 4. It may be possible to employ an air
compressor (not shown) for serving to supply combustion air to the
combustion unit 21 in the place of the air compressor 7.
On starting the operation of the coal gasifying furnace 1, the gasification
reaction will not provide a fuel gas of steady composition but fluctuates
considerably not only in the composition but also in the temperature etc.,
so that the product gas during the warming-up operation will not be
utilized for the fuel gas of the gas turbine burner and thus is to be
treated in accordance with the present invention so as to permit it to be
discharged into the atmosphere. The noxious and combustible gases produced
during the warming-up operation are supplied to the additional combustion
unit 21 where it is burnt out into innoxious state. The combustion gas
resulting therefrom is supplied to the waste heat boiler 8 in order to
recover the sensible heat contained therein. The so treated cooled gas is
wasted into the atmospher through the chimney 9.
It is preferable to operate the additional combustion unit 21 on a
principle of catalytic converter in order to subject the gases fed
thereto, which have in general poor heat of combustion and low
concentrations of combustible components, to an efficient and promoted
chemical reaction. By selecting an adequate catalyst in a suitable amount,
it is possible to attain a stable and efficient conversion without
necessitating any special means for monitoring and for operation.
Due to the acceleration of burning reaction, a lower temperature can be
employed for the catalytic burning as compared with ordinary combustion
without catalyst, whereby occurrence of thermal nitrogen oxides that cause
secondary environmental pollution will be minimized.
Moreover, the temperature of the catalytic combustion gas is nearly equal
to that of the exhaust gas from the gas turnine during its normal run, so
that it can be introduced into the waste heat boiler arranged in a
succeeding portion in the system, without incorporation of any special
temperature-reducing means.
While the pressure in the coal gasifying furnace is lower during the
warming-up operation of the plant, it is possible to restore the pressure
by catalytic burning to such a level, in which it may correspond to the
exhaustion gas pressure from the gas turbine when taking into account of
the possible pressure drop in the catalytic burner.
Now, description will be directed to the second Example shown in FIG. 2.
This Example shows a composite coal gasification-power plant in which the
first aspect of the present invention is combined with the second aspect
of the present invention. Here also, the same reference numerals are
employed for the same elements as shown in FIG. 1 and the explanation of
such elements are therefore omitted.
The noxious and combustible gases released from various safety valves 13
and pressure control valves 14 arranged for the purpose of security
confirmation upon their occasional actuation are once collected in a
pressure vessel 15 and are fed from here to the additional combustion unit
21 to burn them out into an innoxious state. The combustion gas therefrom
is then supplied to the waste heat boiler 8, from which it is discharged
into the atmosphere through the chimney 9 after its sensible heat has been
recovered.
It is of course preferable and falls under the scope of the present
invention that every combustible gas released from, such as relief valves
(not shown), is collected in the pressure vessel 15 and supplied then to
the additional combustion unit 21.
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